This invention relates to an internal combustion engine and, more particularly, to an engine in which a governor vane is pivotally mounted in the path of cooling air which is circulated by a fan driven by the output shaft of the engine. As the rotational speed of the shaft increases and decreases because of varying loads, the governor vane swings back and forth and adjusts the flow of a fuel-air mixture to the combustion chamber of the engine in order to keep the shaft turning at a substantially constant speed.